Compressors are well known technology having numerous applications. It is also known that compressors will be damaged if the compressor blades, rotating at high speed, are hit by heavy objects. Such heavy objects include excessive quantities of oil drops and water drops. Accordingly, a compressor can only operate reliably if the liquid contents of the gas to be compressed is within a maximum acceptable limit.
For compressors operating on dry sites, such as industrial sites, the liquid contents can be separated out from the inlet gas. The separated liquid can be used for any convenient purpose or be discharged after being cleaned if required.
For a compressor located subsea, neither of separation, use and discharge of the liquid is straightforward. The actual location of the compressor can be tens or hundreds of kilometers away from land or surface installations and the depth can be hundreds of meters. Use of the separated liquid, typically oil and possibly water, requires huge investments in equipment and pipes. Discharge of the oil will violate regulations. The equipment for subsea separation and cleaning is very expensive. Currently, collection of sample bottles with an ROV (remotely operated vehicle) and nuclear density gauges are the techniques for determination of liquid in gas volume fraction. The above mentioned high cost and limited availability of technology are disadvantages of the prior art subsea compression technology.
There is a demand for both a system and a method for control of a subsea located compressor, providing improvements with respect to the disadvantages mentioned above.